Precise knowledge of the mechanism involved in the remodeling of the connective tissue components in the periodontium is essential to better understanding of changes in periodontal diseases, orthodontic tooth movement and tooth transplantation or replantation. Like other connective tissues the periodontium is characterized by a relatively abundant extracellular matrix composed in part macromolecules such as collagen, proteinpolysaccharides (proteoglycans) and glycoproteins. The extent of our knowledge of the remodeling of the connective tissue of the periodontal ligament and the gingivae depends on our knowledge of the metabolism of its individual components. The purpose of this project is to use micromethods and isotopic tracers to determine the turnover rates of collagen and acid mucopolysaccharides in the periodontium of the rat. The periodontal ligament and the gingivae will be obtained using microdissection techniques. The turnover rates of collagen will be determined using H3- proline and those of acid mucopolysaccharides by the use of S35-sulfate, and C14-glucosamine. Previous studies using autoradiographic and histochemical techniques have indicated that the connective tissue of the periodontium turns over at rate higher than in other tissues tested. The development and the use of microdissection and microchemical techniques may clarify many questions raised by the autoradiographic and histochemical studies and further open new approaches to the study of periodontium in health and disease.